Chapter Eleven - Partner preference in the legume-rhizobia symbiosis and impact on legume inoculation strategies.

Legumes interact with diverse soil bacteria of the genus Rhizobium to form dinitrogen (N2)-fixing symbiotic root nodules. This symbiotic interaction occurs under plant nitrogen (N)-deficit and only between compatible partners. When young nodules are formed, bacteroids begin to fix atmospheric N2 and provide ammonium to the plant which in return provides phytosynthates to the bacteria. Ability and Competitiveness to Form root Nodules (AFN and CFN) within natural populations have a strong impact on early partner choice. In soil, there are frequently multiple compatible partners and legume roots are often colonized by multiple rhizobia displaying different Symbiotic N2 Fixation (SNF) efficiencies. In mature nodules, Post-Infection Partner Preference (PIPP) shape partner choice by favoring effective symbiotic N2fixing structures to the expense of inefficient ones. Little is known about mechanisms involved in legume-rhizobium partner choices despite the relevance of this trait to design new strategies to improve inoculation of legume crops. [ABSTRACT FROM AUTHOR]